The glycolytic pathway in the human parasite, Entamoeba histolytica, presents a striking deviation from the usual Embden- Meyerhof pathway between glucose and pyruvate. The last enzyme of the sequences, pyruvate kinase, is lacking in the parasite. In its stead is found an enzyme called pyruvate phosphate dikinase which converts P- enolpyruvate (PEP) to pyruvate as follows: PEP plus AMP plus PPi yields pyruvate plus ATP plus Pi (I). Inorganic pyrophosphate (PPi) for the above reaction is apparently supplied by a second enzyme acting also on PEP. It is PEP carboxy-transphosphorylase, catalyzing the following reaction: PEP plus CO2 plus Pi yields Oxaloacetate plus PPi (II). Molecules of PEP which are converted to oxaloacetate may be transformed further to pyruvate via the lower branch of the scheme: upper branch: PEP in the presence of pyruvate phosphate dikinase yields pyruvate or lower branch: PEP can be converted to pyruvate via a different route (PEP plus PEP carboxy-transphosphorylase yields oxaloacetate which can be further converted to malate and then pyruvate by two other amebal enzymes). It is now proposed to show if the abundant amebal enzymes which catalyze steps I - IV individually may function as a system in the postulated direction in the living cell. Amebae will be tested to learn if they are capable of carrying on gluconeogenesis. The four enzymes will be individually purified and their properties studied. Reaction kinetics will reveal if the four enzymes are capable of forming a compatible system for conversion of PEP to pyruvate at the rate demanded. In living cells a steady state PPi pool should be reached and 32p from orthophosphate should rapidly be incorporated into this pool. Label from glucose should appear simultaneously in pyruvate oxaloacetate and malate, while label from CO2 should appear, initially, only in the last two. Finally, the mechanism of action of the dikinase and transphosphorylase enzymes will be studied.